Microsilica powder (Microsilica, silica Fume) is a by-product of the ferrosilicon production process in an electric arc furnace. Microsilica powder has super pozzolanic properties and is widely used in concreting related to the construction of marine structures, high-strength structures, and all structures exposed to chemical attacks, especially chloride and sulfate ions. Research has shown that the obtained dust known as microsilica has found various applications and gained economic value and is no longer considered a production waste but rather a by-product.
Applications of Microsilica Based on Consumption Amount
The use of microsilica dust in concrete and cement has greatly increased in recent years. Microsilica acts as a pozzolan by uniformly dispersing and increasing the volume of hydration products in concrete. Moreover, due to its fine particles, it acts as a filler, reducing the pore size in the cement paste. As a result, using microsilica in concrete creates the following properties:
- Increased compressive strength
- Increased abrasion resistance
- Reduced permeability
- Resistance to sulfates
- Corrosion resistance
The typical consumption amount of microsilica in concrete is 5 to 20 percent of the cement weight, though values up to about 40 percent have also been reported. The efficiency of microsilica is about three times that of cement; in other words, one kilogram of microsilica can replace three kilograms of cement without reducing quality or strength. This phenomenon can be considered a factor in reducing cement consumption but does not eliminate the need for cement.
The presence of microsilica particles in the concrete mix reduces the amount of water needed for mixing. Therefore, the resulting concrete is more stable and adhesive, and the concreting process is carried out more easily. Microsilica can also be directly used in cement production.
When polymer products are extruded, microsilica can be used as an effective filler and reinforcement to improve impact strength and stiffness. Microsilica also improves the production process by producing smoother surfaces and enhancing manufacturability.
Various types of microsilica refractories can be used in the production of refractory concretes made from calcium aluminate cements. At the same time, this material can be used in the production of other types of refractory materials. In these cases, the use of microsilica improves ceramic bonding and significantly enhances product properties.
Microsilica with high reactivity can be used to produce various types of silicates. Microsilica products are also used as coating powders, insulating powders, auxiliary materials in catalytic protection systems, and for selective ion adsorption in chemical industries. Considering the expansion of ferroalloy production and the increase in microsilica dust volume, further applications are expected in industries that require both finesse and strength simultaneously.
The chemical composition of microsilica is shown in the table below:
| CaO | S | MgO | K₂O | Na₂O | C | Fe₂O₃ | Al₂O₃ | SiO₂ |
|---|---|---|---|---|---|---|---|---|
| 0.1–0.5 | 0.1–0.4 | 0.5–2.0 | 1.0–3.0 | 0.4–1.5 | 0.5–2.5 | 0.2–1.5 | 0.4–1.0 | 86–94 |
